Bow and crossbow archers constantly seek ways to improve the accuracy and reliability of their bows and crossbows. One way to improve accuracy and reliability is to control the orientation of the projectile (e.g., an arrow or bolt) when it is launched from the bow or crossbow. In an archery bow (e.g., a compound bow or recurve bow), the fletchings or vanes of the arrow should be oriented so that they have minimal interference with the cables, arrow rest, and riser as the arrow is launched. Similarly, in a crossbow the fletchings or vanes of the bolt must be properly oriented to avoid conflicting contact with the rails as the bolt is launched.
The nock at the trailing end of an arrow or bolt may also affect the reliability of the bow. For example, it may be possible to dry fire a bow or crossbow (i.e., release the string without launching an arrow) if the bowstring is able to slip laterally around the trailing end of the arrow and move along the shaft of the projectile when the bowstring is released. When a dry fire occurs, the energy that otherwise would be transmitted to the projectile is absorbed by the bow or crossbow, which can cause undesirable consequences.
The trailing end of an arrow or bolt for a crossbow, for example, most often includes a nock to help orient the projectile relative to the crossbow and to keep the bowstring secured to the projectile until it reaches the proper release position. A half moon nock, for example, may be attached to a bolt so that when a crossbow's bowstring extends across and within the half-moon shaped groove of the nock, an index vane of the bolt is properly oriented between rails of the crossbow. When the bowstring is released, the C-shaped or V-shaped groove at the end of the nock keeps the bowstring aligned directly with the longitudinal axis of the shaft of the bolt to avoid a situation where the bowstring slips to one side of the neck when the bolt is launched from the crossbow. The force of the bowstring is therefore efficiently and properly transferred to the projectile.
However, some of these types of nocks have drawbacks, nocks and vanes are typically secured to the bolt shafts as part of an assembly process performed by manufacturers or by end-users. These processes are susceptible to imperfections and errors that can affect the nock's orientation and performance. If a vane or half-moon nock is not attached correctly to a bolt shaft, the index vane may not be oriented to the bowstring properly when loaded into a crossbow. As such, the vane may undesirably drag against the crossbow rails when the bowstring is released or the bowstring will not seat and engage the nock correctly. A misaligned nock may cause the bolt to be pushed to one side during the launch process, thereby affecting the bolt's flight and potentially causing a dry fire. Additionally, even if the nock is properly attached to the shaft, the archer load the bolt incorrectly (e.g., using the wrong vane as an index vane) and may thereby inhibit proper interaction between the nock and the bowstring.
Some nock makers have engineered nocks with multiple rear groove shapes in order to reduce the chance that a bolt is improperly loaded into the crossbow. These nocks are nevertheless still vulnerable to misalignment by the manufacturer or end user and may not provide enough grip to keep the bowstring seated against the bolt, so the potential for dry fires is still present. Crossbows conventionally use some kind of anti-dry fire (ADF) mechanism to prevent release of the bowstring unless a bolt is loaded onto the crossbow, but such devices do not determine the orientation (rotational or longitudinal) of the bolt relative to the crossbow, and thus an improperly loaded bolt may result in a dry fire. There is therefore a need for improvements to existing archery nocks and anti-dry fire devices.